Light emitting device and optical device using the same

ABSTRACT

A light emitting device which can be easily manufactured and can control the positions of light emission precisely, and an optical device. A first and second light emitting elements are formed on one face of a supporting base. The first light emitting element has an active layer made of GaInN mixed crystal on a GaN-made first substrate on the side thereof on which the supporting base is disposed. The second light emitting element has lasing portions on a GaAs-made second substrate on the side thereof on which the supporting base is disposed. Since the first and second light emitting elements are not grown on the same substrate, a multiple-wavelength laser having the output wavelength of around 400 nm can be easily obtained. Since the first substrate is transparent in the visible region, the positions of light emitting regions in the first and second light emitting elements can be precisely controlled by lithography.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a light emitting device having aplurality of light emitting elements, and an optical device using thesame.

[0003] 2. Description of the Related Art

[0004] In recent years, in the field of light emitting devices, asemiconductor laser (LD; laser diode) in which a plurality of lightemitting portions of different output wavelengths are formed on the samesubstrate (or board) (hereinafter referred to as a multiple-wavelengthlaser) is actively developed. An example of such a multiple-wavelengthlaser is, as shown in FIG. 1, obtained by forming a plurality of lightemitting portions of different output wavelengths on a single chip (whatis called a monolithic type multiple-wavelength laser). In themultiple-wavelength laser, for example, a lasing portion 201 formed bygrowing layers of semiconductor materials of the system AlGaAs by vaporphase epitaxy and a lasing portion 202 formed by growing layers ofsemiconductor materials of the system AlGaInP are disposed side by sideon one face of a substrate 212 made of GaAs (gallium arsenide) with anisolation groove 211 between them. In this case, the output wavelengthof the lasing portion 201 is in the range of the order of 700 nm (forexample, 780 nm) and that of the lasing portion 202 is in the range ofthe order of 600 nm (for example, 650 nm).

[0005] Except for the structure shown in FIG. 1, a structure (what iscalled a hybrid type multiple-wavelength laser) in which a plurality ofsemiconductor lasers LD₁ and LD₂ having different output wavelengths aremounted side by side on a board 221 has been also proposed. Theabove-mentioned monolithic-type laser is, however, more effective incontrolling the light emitting point intervals with high accuracy.

[0006] These multiple-wavelength lasers are used, for example, as laserlight sources of optical disk drives. At present, in an optical diskdrive, semiconductor laser light in the range of the order of 700 nm isgenerally used for optical playback of CD (Compact Disk) recording orfor optical recording/playback using recordable optical disks such asCD-Rs (recordable CDs), CD-RWs (rewritable CDs) or MDs (Mini Disks).Semiconductor laser light in the range of the order of 600 nm is usedfor optical recording/playback using DVDs (Digital Versatile Disks). Bymounting a multiple-wavelength laser as described above on an opticaldisk drive, optical recording/playback becomes possible with respect toany existing optical disks. Moreover, the lasing portions 201 and 202are disposed side by side on the same substrate (as for thesemiconductor lasers LD₁ and LD₂ of the hybrid type, on the same board),only one package is necessary for the laser light source. The number ofparts of an optical system such as an objective lens and a beam splitterfor optical recording/playback using various optical disks is decreasedto simplify the configuration of the optical system. Thus, reduction insize and cost of an optical disk drive can be achieved.

[0007] Meanwhile, in recent years, the demand for further growth ofoptical recording area density by using semiconductor lasers of shorteroutput wavelengths has been growing. Heretofore known materials ofsemiconductor lasers addressing the demand are Group III-V compoundsemiconductors of the nitride system (hereinbelow, also calledsemiconductors of the system GaN) typified by GaN, AlGaN mixed crystals,and GaInN mixed crystals. Semiconductor lasers using semiconductors ofthe system GaN are capable of light emission at a wavelength of around400 nm, which is regarded as the limit wavelength at which opticalrecording/playback is done using an optical disk and an existing opticalsystem, and therefore, they receive much attention as light sources ofnext-generation optical recording/playback apparatuses. It is alsoexpected as light sources of full-color displays using three primarycolors of RGB. Thus, development of multiple-wavelength lasers withlasing portions of the system GaN is desired.

[0008] As an example of related-art multiple-wavelength lasers withlasing portions of the system GaN, as shown in FIG. 3, amultiple-wavelength laser is proposed in which the lasing portion 201 ofthe system AlGaAs, the lasing portion 202 of the system AlGaInP, and thelasing portion 203 of the system GaN are formed side by side on one faceof a substrate 231 made of SiC (silicon carbide) with isolation grooves211 a and 211 b between them (refer to Publication of JapaneseUnexamined Patent Application No. Hei-11-186651).

[0009] In the case of fabricating the monolithic typemultiple-wavelength laser, however, there is a problem such that it isdifficult to integrate lasing portions on the same substrate as one chipdue to, for example, a large difference in lattice constant between thematerials of the system GaN and the materials of the system AlGaAs orAlGaInP.

[0010] The hybrid type multiple-wavelength laser has, as alreadydescribed, a problem of poor controllability on the light emitting pointintervals. The side-by-side arrangement of three or more semiconductorlasers causes an inconvenience such that the controllability on thelight emitting point intervals further deteriorates.

SUMMARY OF THE INVENTION

[0011] The invention has been achieved in consideration of the problemsand its object is to provide a light emitting device which can be easilymanufactured and can control the position of light emission withaccuracy, and an optical device using the light emitting device.

[0012] A light emitting device according to the invention has aplurality of light emitting devices stacked on one face of a supportingbase

[0013] Another light emitting device according to the invention has: asupporting base; a first light emitting element having a firstsubstrate, provided on one face of the supporting base; and a secondlight emitting element having a second substrate, provided on the sideof the first light emitting element opposite to the supporting base.

[0014] An optical device according to the invention has a light emittingdevice in which a plurality of light emitting elements are stacked onone face of a supporting base.

[0015] In another optical device according to the invention, a lightemitting device is mounted. The light emitting device comprises: asupporting base; a first light emitting element having a firstsubstrate, provided on one face of the supporting base; and a secondlight emitting element having a second substrate, provided on the sideof the first light emitting element opposite to the supporting base.

[0016] In the light emitting device according to the invention and theother light emitting device according to the invention, a plurality oflight emitting elements are stacked on one face of a supporting base.Therefore, the devices are easily manufactured and the light emittingregions are disposed with high precision.

[0017] In the optical device according to the invention and the otheroptical device according to the invention, they have the light emittingdevice according to the invention in which light emitting regions aredisposed with high precision. This contributes to size reduction.

[0018] Other and further objects, features and advantages of theinvention will appear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a cross section showing an example of the configurationof a related-art light emitting device.

[0020]FIG. 2 is a cross section showing another example of theconfiguration of a related-art light emitting device.

[0021]FIG. 3 is a cross section showing still another example of theconfiguration of a related-art light emitting device.

[0022]FIG. 4 is a cross section showing the configuration of a lightemitting device according to a first embodiment of the invention.

[0023]FIG. 5 is a partly-exploded perspective view showing theconfiguration of a package in which the light emitting device shown inFIG. 4 is enclosed.

[0024]FIGS. 6A and 6B are cross sections for explaining a method ofmanufacturing the light emitting device shown in FIG. 4.

[0025]FIGS. 7A and 7B are cross sections for explaining a manufacturingprocess subsequent to FIG. 6B.

[0026]FIGS. 8A and 8B are cross sections for explaining a manufacturingprocess subsequent to FIG. 7B.

[0027]FIGS. 9A and 9B are cross sections for explaining a manufacturingprocess subsequent to FIG. 8B.

[0028]FIG. 10 is a diagram showing the configuration of an optical diskrecording/playback apparatus using the light emitting device shown inFIG. 4.

[0029]FIG. 11 is a cross section showing the construction of a lightemitting device according to a second embodiment of the invention.

[0030]FIGS. 12A and 12B are cross sections for explaining a method ofmanufacturing a light emitting device shown in FIG. 11.

[0031]FIGS. 13A and 13B are cross sections for explaining amanufacturing process subsequent to FIG. 12B.

[0032]FIG. 14 is a cross section for explaining a manufacturing processsubsequent to FIG. 13B.

[0033]FIG. 15 is a plan view showing a schematic configuration of adisplay apparatus using the light emitting device illustrated in FIG.11.

[0034]FIG. 16 is a diagram showing the configuration of a main portionof a driving circuit of the display apparatus illustrated in FIG. 15.

[0035]FIG. 17 is a cross section showing the configuration of a lightemitting device according to a third embodiment of the invention.

[0036]FIGS. 18A and 18B are cross sections for explaining a method ofmanufacturing the light emitting device illustrated in FIG. 17.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Embodiments of the invention will be described in detailhereinbelow with reference to the drawings.

First Embodiment

[0038]FIG. 4 shows the sectional structure of a light emitting device10A according to a first embodiment of the invention. The light emittingdevice 10A has a supporting base 11, a first light emitting element 20disposed on one face of the supporting; base 11, and a second lightemitting element 30 disposed on the side of the first light emittingelement 20 opposite to the supporting base 11.

[0039] The supporting base 11 is made of a metal such as copper (Cu) andserves as a heat sink for dissipating heat generated by the first andsecond light emitting elements 20 and 30. The supporting base 11 iselectrically connected to an external power source (not shown) and alsohas the role of electrically connecting the first light emitting element20 to the external power source.

[0040] The first light emitting element 20 is, for example, asemiconductor laser capable of emitting light having a wavelength ofaround 400 nm. The first light emitting element 20 has a configurationin which an n-type cladding layer 22, an active layer 23, a degradationpreventing layer 24, a p-type cladding layer 25, and a p-side contactlayer 26 which are made of a Group III-V compound semiconductor of thenitride system are laid one upon another in the order named on a firstsubstrate 21 made of a Group III-V compound semiconductor of the nitridesystem, on the side thereof on which the supporting base 11 is disposed.The Group III-V compound semiconductor of the nitride system refers to amaterial containing at least one of Group 3B elements in theshort-period type periodic table and at least nitrogen (N) from Group 5Belements in the short-period type periodic table.

[0041] Specifically, the first substrate 21 is made of, for example,n-type GaN doped with silicon (Si) as an n-type impurity, and itsthickness in the deposition direction (hereinbelow, simply referred toas thickness) is, for example, 80 to 100 μm. GaN is a transparentmaterial in the visible region (about 380 to 800 nm). GaN is a materialhaving excellent thermal conductivity as high as about 1.3 W/(cm·K). Byusing the characteristic, the first substrate 21 functions as a heatsink which dissipates heat generated by the second light emittingelement 30.

[0042] The n-type cladding layer 22 is, for example, 1 μm thick and ismade of n-type AlGaN (for example, Al_(0.08)G_(0.92)N) mixed crystaldoped with silicon as an n-type impurity. The active layer 23 is, forexample, 30 nm thick and has a multiple quantum well structure includinga well layer and a barrier layer made of Ga_(x)In_(1-x)N (where, x≧0)having different compositions. The active layer 23 functions as a lightemitting portion.

[0043] The degradation preventing layer 24 is, for example, 20 nm thickand is made of p-type AlGaN (such as Al_(0.2)Ga_(0.8)N) mixed crystaldoped with magnesium (Mg) as a p-type impurity. The p-type claddinglayer 25 is, for example, 0.7 μm thick and is made of p-type AlGaN (suchas Al_(0.08)Ga_(0.92)N) mixed crystal doped with magnesium as a p-typeimpurity. The p-side contact layer 26 is, for example, 0.1 μm thick andis made of p-type GaN doped with magnesium as a p-type impurity.

[0044] A part of the p-type cladding layer 25, and the p-side contactlayer 26 are formed in a narrow strip shape extending in the cavitydirection (perpendicular direction to the drawing sheet in FIG. 4) so asto produce what is called a laser stripe, thereby restricting a current.The p-side contact layer 26 is provided in the center portion in thedirection (direction indicated by the arrow A in FIG. 4) perpendicularto the cavity direction. Side faces of the p-side contact layer 26 and aside of the p-type cladding layer 25 opposite to the degradationpreventing layer 24 are covered with an insulating layer 27 made ofsilicon dioxide (SiO₂) or the like. The region in the active layer 23corresponding to the p-side contact layer 26 is a light emitting region.

[0045] On the side of the p-side contact layer 26 opposite to the p-typecladding layer 25, a p-side electrode 28 is formed. The p-side electrode28 is formed by depositing palladium (Pd), platinum (Pt) and gold (Au)in order from the p-side contact layer 26 side and is electricallyconnected to the p-side contact layer 26. The p-side electrode 28 isalso electrically connected to the supporting base 11 via an adhesivelayer 12. The adhesive layer 12 is made of, for example, an alloy ofgold (Au) and tin (Sn), or tin.

[0046] On the side of the first substrate 21 opposite to the supportingbase 11, an n-side electrode 29 is provided in correspondence with alasing portion 50, which will be described hereinlater. The n-sideelectrode 29 is obtained by, for example, depositing titanium (Ti) andaluminum in order from the first substrate 21 side and alloying thedeposited materials by heat treatment, and is electrically connected tothe first substrate 21. The n-side electrode 29 also has the function asa wire for connecting the lasing portion 50 to the external powersource. On the side of the first substrate 21 opposite to the supportingbase 11, a wiring layer 13 for electrical connection to a lasing portion40 of the second light emitting element 30 is formed with an insulatingfilm 14 in between. The wiring layer 13 is made of, for example, ametal. Details of the lasing portion 40 will be given hereinlater.

[0047] Further, a pair of side faces at the ends in the cavity directionof the first light emitting element 20 serve as two end planes of thecavity. A pair of reflecting mirror films (not shown) are formed on thepair of end planes of the cavity. One of the pair of reflecting mirrorfilms is set so as to reflect light produced in the active layer 23 athigh reflectance, and the other film is set to reflect light atreflectance lower than the above reflectance, so that light goes outfrom the other film.

[0048] The second light emitting element 30 has, for example, a secondsubstrate 31, the lasing portion 40 and the lasing portion 50. Thelasing portion 40 is capable of emitting light in the range of the orderof 700 nm (for example, 780 nm) and is formed on the second substrate 31on the side thereof on which the supporting base 11 is disposed, with abuffer layer 32 in between. The lasing portion 50 is capable of emittinglight in the range of the order of 600 nm (for example, 650 nm) and isformed on the second substrate 31 on the side thereof on which thesupporting base 11 is disposed, with the buffer layer 32 in between. Thesecond substrate 31 is, for example, about 100 μm thick and is made ofn-type GaAs doped with silicon as an n-type impurity. The buffer layer32 is, for example, 0.5 μm thick and is made of n-type GaAs doped withsilicon as an n-type impurity. The lasing portions 40 and 50 aredisposed with a space of, for example, about 200 μm or less so thattheir cavity directions are aligned with that of the first lightemitting element 20 and the p-side contact layer 26 in the first lightemitting element 20 is positioned between the lasing portions 40 and 50.Specifically, the space between a light emitting region of the lasingportion 40 and a light emitting region of the lasing portion 50 is about120 μm, and the light emitting region of the first light emitting device20 is positioned just in the middle of the light emitting regions of thelasing portions 40 and 50. Details of the light emitting regions of thelasing portions 40 and 50 will be given later.

[0049] The lasing portion 40 has a configuration in which an n-typecladding layer 41, an active layer 42, a p-type cladding layer 43, and ap-type cap layer 44 are laid one upon another in the order named fromthe second substrate 31 side. Each of the layers is made of, forexample, a Group III-V compound semiconductor containing at leastgallium (Ga) from Group 3B elements in the short-period type periodictable and at least arsenide (As) from Group 5B elements in theshort-period type periodic table.

[0050] Specifically, the n-type cladding layer 41 is, for example, 1.5μm thick and is made of n-type AlGaAs mixed crystal doped with siliconas an n-type impurity. The active layer 42 is, for example, 40 nm thickand has a multiple quantum well structure including a well layer and abarrier layer made of Al_(x)Ga_(1-x)As (where, x≧0) having differentcompositions. The active layer 42 functions as a light emitting portionand the wavelength of the output light is, for instance, in the range ofthe order of 700 nm. The p-type cladding layer 43 is, for example, 1.5μm thick and is made of p-type AlGaAs mixed crystal doped with zinc as ap-type impurity. The p-type cap layer 44 is, for example, 0.5 μm thickand is made of p-type GaAs doped with zinc as a p-type impurity.

[0051] A part of the p-type cladding layer 43, and the p-type cap layer44 are formed in a narrow strip shape extending in the cavity direction,thereby restricting a current. On both sides of the strip portion,current block regions 45 are provided. The region of the active layer 42corresponding to the p-side cap layer 44 serves as a light emittingregion.

[0052] On the side of the p-type cap layer 44 opposite to the p-typecladding layer 43, a p-side electrode 46 is formed. The p-side electrode46 is formed by, for example, depositing titanium, platinum and gold inorder from the side of the p-side cap layer 44 and alloying thedeposited materials by heat treatment, and is electrically connected tothe p-type cap layer 44. The p-side electrode 46 is also electricallyconnected to the wiring layer 13 via an adhesive layer 15. The adhesivelayer 15 is made of, for example, a material similar to that of theadhesive layer 12.

[0053] The lasing portion 50 has a configuration in which an n-typecladding layer 52, an active layer 53, a p-type cladding layer 54, and ap-type cap layer 55 are laid one upon another in the order named fromthe side of the second substrate 31, with a buffer layer 51 in between.Each of the layers is made of, for example, a Group III-V compoundsemiconductor containing at least indium (In) from Group 3B elements inthe short-period type periodic table and at least phosphorus (P) fromGroup 5B elements in the short-period type periodic table.

[0054] Specifically, the buffer layer 51 is, for example, 0.5 μm thickand is made of n-type InGaP mixed crystal doped with silicon as ann-type impurity. The n-type cladding layer 52 is, for example, 1.5 μmthick and is made of n-type AlGaInP mixed crystal doped with silicon asan n-type impurity. The active layer 53 is, for example, 35 nm thick andhas a multiple quantum well structure including a well layer and abarrier layer made by Al_(x)Ga_(y)In_(1-x-y)P (where x≧0 and y≧0) havingdifferent compositions. The active layer 53 functions as a lightemitting portion. The p-type cladding layer 54 is, for example, 1.0 μmthick and is made of p-type AlGaInP mixed crystal doped with zinc as ap-type impurity. The p-type cap layer 55 is, for example, 0.5 μm thickand is made of p-type GaAs doped with zinc as a p-type impurity.

[0055] A part of the p-type cladding layer 54 and the p-type cap layer55 are formed in a narrow strip shape to produce a current-restrictingarea extending in the cavity direction. On both sides of the stripportion, current block regions 56 are provided. The region of the activelayer 53 corresponding to the p-side cap layer 55 serves as a lightemitting region.

[0056] On the side of the p-type cap layer 55 opposite to the p-typecladding layer 54, a p-side electrode 57 is provided. The p-sideelectrode 57 is electrically connected to the p-type cap layer 55 andhas, for example, the configuration similar to that of the p-sideelectrode 46. The p-side electrode 57 is also electrically connected tothe n-side electrode 29 of the first light emitting element 20 via anadhesive layer 16 made of a material similar to that of the adhesivelayer 15.

[0057] On the side of the second substrate 31 opposite to the supportingbase 11, an n-side electrode 33 of the lasing portions 40 and 50 isformed. The n-side electrode 33 is obtained by, for example, depositingan alloy of gold and germanium (Ge), nickel, and gold in order from theside of the second substrate 31 and alloying the deposited materials byheat treatment.

[0058] Further, a pair of side faces at the ends in the cavity directionof the second light emitting element 30 serve as two end planes of thecavity. A pair of reflecting mirror films (not shown) are formed on thepair of end faces of the cavity of each of the lasing portions 40 and50. The relation of reflectance between the pairs of reflecting mirrorfilms is set so as to correspond to that between the pair of reflectingmirror films provided in the first light emitting element 20. Light isemitted from the same side of the first light emitting element 20 andthe lasing portions 40 and 50 of the second light emitting element 30.

[0059] The light emitting device 10A having such a configuration is, forexample as shown in FIG. 5, enclosed in a package 1 for practical use.The package 1 has, for example, a disk-shaped supporting body 2 and acover body 3 provided on the side of one face of the supporting body 2.Inside the cover body 3, the supporting base 11 is supported by thesupporting body 2 and the light emitting device 10A is enclosed. Lightemitted from the light emitting device 10A goes out from a window 3 a ofthe cover body 3.

[0060] The package 1 is provided with a plurality of conductive pins 4 ato 4 d, and the pin 4 a is electrically connected to the supporting base11. The other pins 4 b to 4 d, for example, penetrate the supportingbody 2 via insulating rings 5 b to 5 d respectively and extend from theinside of the cover body 3 to the outside. The wiring layer 13 iselectrically connected to the pin 4 b via a wire 6 b. The n-sideelectrode 29 is electrically connected to the pin 4 cvia a wire 6 c. Then-side electrode 33 is electrically connected to the pin 4 d via a wire6 d. Although the package 1 having the four pins 4 a to 4 d is describedhere as an example, the number of pins can be set as appropriate. Forexample, when the wiring layer 13 and the supporting base 11 areconnected to each other via a wire, the pin 4 b is unnecessary and thenumber of pins becomes three.

[0061] Such a light emitting device 10A can be manufactured as follows.FIGS. 6A to 9B show the manufacturing steps of the method ofmanufacturing the light emitting device 10A.

[0062] First, as shown in FIG. 6A, for example, the first substrate 21made of n-type GaN having a thickness of about 400 μm is prepared. Onthe surface of the first substrate 21, the n-type cladding layer 22 madeof n-type AlGaN mixed crystal, the active layer 23 made of InGaN mixedcrystal, the degradation preventing layer 24 made of p-type AlGaN mixedcrystal, the p-type cladding layer 25 made of p-type AlGaN mixedcrystal, and the p-side contact layer 26 made of p-type GaN are grown inorder by MOCVD. At the time of growing each of the layers, thetemperature of the first substrate 21 is adjusted to, for example, 750°C. to 1100° C.

[0063] Referring to FIG. 6B, a mask (not shown) is formed on the p-sidecontact layer 26. The upper layer portion of each of the p-side contactlayer 26 and the p-type cladding layer 25 is selectively etched into anarrow strip shape, and thus the p-type cladding layer 25 is exposed.Subsequently, by using the not-shown mask on the p-side contact layer26, the insulating layer 27 is formed so as to cover the surface of thep-type cladding layer 25 and the side faces of the p-side contact layer26.

[0064] After forming the insulating layer 27, on and around the surfaceof the p-side contact layer 26, for example, palladium, platinum, andgold are vapor-deposited in order, and the p-side electrode 28 isformed. Further, in order to easily cleave the first substrate 21 in aprocess which will be described hereinlater, the rear face side of thefirst substrate 21 is, for example, lapped and polished so that thethickness of the first substrate becomes about 100 μm.

[0065] Subsequently, on the rear face side of the first substrate 21,the insulating film 14 is formed in correspondence with the position ofthe lasing portion 40, and the wiring layer 13 is formed on theinsulating film 14. In correspondence with the position of the lasingportion 50, for example, titanium and aluminum are vapor-deposited inorder, and the n-side electrode 29 is formed. Specifically, each of thewiring layer 13 and the n-side electrode 29 is formed in a positionapart from the p-side contact layer 26 by about 60 μm. In theembodiment, the first substrate 21 is made of GaN which is transparentin the visible region, and layers which are made of Group III-V compoundsemiconductors and are also transparent in the visible region arestacked on the first substrate 21. Therefore, the position of the p-sideelectrode 28 can be observed from the first substrate 21 side and thepositioning in the lithography process can be performed with highprecision. That is, the positions in which the wiring layer 13 and then-side electrode 29 are formed can be precisely controlled. Since GaN ofthe first substrate 21 is hard, even when the thickness of the firstsubstrate 21 is about 100 μm, there is no possibility that the firstsubstrate 21 is cracked or the like in the lithography process.

[0066] After forming the wiring layer 13 and the n-side electrode 29,heat treatment is performed to thereby alloy the n-side electrode 29.After that, although not shown, the first substrate 21 is, for example,cleaved perpendicular to the longitudinal direction of the p-sideelectrode 28 in a predetermined width and a pair of reflecting mirrorfilms are formed on the cleaved faces. In such a manner, the first lightemitting element 20 is fabricated.

[0067] As shown in FIG. 7A, for example, the second substrate 31 made ofn-type GaAs having a thickness of about 350 μm is prepared. On thesurface of the second substrate 31, the buffer layer 32 made of n-typeGaAs, the n-type cladding layer 41 made of n-type AlGaAs mixed crystal,the active layer 42 made of Al_(x)Ga_(1-x)As (where x≧0) mixed crystal,the p-type cladding layer 43 made of p-type AlGaAs mixed crystal, andthe p-type cap layer 44 made of p-type GaAs are grown in order by MOCVD.At the time of growing each of the layers, the temperature of the secondsubstrate 31 is adjusted to, for example, 750° C. to 800° C.

[0068] As shown in FIG. 7B, a resist film R₁ is formed on the p-type caplayer 44 in correspondence with the region in which the lasing portion40 is to be formed. After that, by using the resist film R₁ as a mask,the p-type cap layer 44 is selectively removed by using, for example,sulfuric-acid-based etchant, and the portion which is not covered withthe resist film R₁ of the p-type cap layer 44, p-type cladding layer 43,active layer 42, and n-type cladding layer 41 is selectively removed byusing hydrofluoric-acid-based etchant. After that, the resist film R₁ isremoved.

[0069] Subsequently, as shown in FIG. 8A, by MOCVD for example, thebuffer layer 51 made of n-type InGaP mixed crystal, the n-type claddinglayer 52 made of n-type AlGaInP mixed crystal, the active layer.53;madeof Al_(x)Ga_(y)In_(1-x-y)P (where x≧0 and y≧0) mixed crystal, the p-typecladding layer 54 made of p-type AlGaInP mixed crystal, and the p-typecap layer 55 made of p-type GaAs are grown in order. At the time ofgrowing each of the layers, the temperature of the second substrate 31is adjusted to, for example, about 680° C.

[0070] After that, as shown in FIG. 8B, a resist film R₂ is formed onthe p-type cap layer 55 in correspondence with the region in which thelasing portion 50 is to be formed. By using the resist film R₂ as amask, the p-type cap layer 55 is selectively removed by using, forexample, sulfuric-acid-based etchant, and the p-type cladding layer 54,active layer 53, and n-type cladding layer 52 are selectively removed byusing phosphoric-acid-based etchant and hydrochloric-acid-based etchant.The buffer layer 51 is selectively removed by usinghydrochloric-acid-based etchant. After that, the resist film R₂ isremoved.

[0071] After removing the resist film R₂, as shown in FIG. 9A, forexample, a narrow strip-shaped mask (not shown) is formed on the p-typecap layers 44 and 55, and an n-type impurity such as silicon isintroduced into the p-type cap layers 44 and 55 and an upper layerportion of the p-type cladding layers 43 and 54 by ion implantation. Theimpurity introduced regions are insulated and become the current blockregions 45 and 56. In this case, since the positions of the p-type caplayers 44 and 55 are defined by using lithography, the positions can becontrolled accurately.

[0072] After forming the current block regions 45 and 56, as shown inFIG. 9B, for example, nickel, platinum, and gold are vapor-deposited inorder on and around the p-type cap layers 44 and 55 to form the p-sideelectrodes 46 and 57. Further, by lapping and polishing the rear faceside of the second substrate 31, the thickness of the second substrate31 is set to, for example, about 100 μm. Subsequently, for example, analloy of gold and germanium, nickel, and gold are vapor-deposited inorder on the rear face side of the second substrate 31 to thereby formthe n-side electrode 33 common to the lasing portions 40 and 50. Afterthat, heat treatment is performed to alloy the p-side electrodes 46 and57 and the n-side electrode 33. Further, although not shown, forexample, the second substrate 31 is cleaved in predetermined widthperpendicular to the longitudinal direction of the p-side electrodes 46and 57 and a pair of reflecting mirror films are formed on the cleavedfaces. In such a manner, the second light emitting element 30 is formed.

[0073] After forming the first and second light emitting elements 20 and30 as described above, the supporting base 11 is prepared. For example,by the adhesive layer 12, the insulating layer 27 and the p-sideelectrode 28 of the first light emitting element 20 and the supportingbase 11 are attached to each other. For example, by the adhesive layer15, the p-side electrode 46 of the second light emitting element 30 andthe wiring layer 13 are attached to each other. For example, by theadhesive layer 16, the p-side electrode 57 in the second light emittingelement 30 and the p-side electrode 29 in the first light emittingelement 20 are attached to each other. In such a manner, the lightemitting device 10A shown in FIG. 4 is completed.

[0074] Since the second light emitting element 30 is disposed on thefirst light emitting element 20 so as to make the wiring layer 13 andthe n-side electrode 29 formed with high positioning accuracy by using ahigh-precision lithography technique correspond to the p-type caplayers. 44 and 55 similarly formed with high positioning accuracy byusing a high-precision lithography technique, the positions of the lightemitting regions are also accurately controlled.

[0075] In the case of simultaneously attaching the supporting base 11 tothe first light emitting element 20, and attaching the, first and secondlight emitting elements 20 and 30, it is preferable to form the adhesivelayers 12, 15 and 16 by using the same material. In the case ofperforming adhesion separately, it is preferable to form an adhesivelayer to be attached first by using a material having a melting pointhigher than that of a material of an adhesive layer to be attachedlater. Specifically, the adhesive layer to be attached first is made ofan alloy of gold and tin, and the adhesive layer to be attached later ismade of tin. Thus, the adhesion can be excellently performed in each ofthe times without heating the layers more than necessary.

[0076] The light emitting device 10A is enclosed in the package 1 asshown in FIG. 5 and operates as follows.

[0077] In the light emitting device 10A, when a voltage is appliedbetween the n-side electrode 29 and the p-side electrode 28 in the firstlight emitting element 20 via the pins 4 cand 4 a of the package 1, acurrent is passed to the active layer 23, light is emitted byrecombination of electrons and holes, and light having a wavelength ofaround 400 nm is emitted from the first light emitting element 20. Whena predetermined voltage is applied between the n-side electrode 33 inthe second light emitting element 30 and the p-side electrode 46, acurrent is passed to the active layer 42, light is emitted byrecombination of electrons and holes, and light having a wavelength inthe band on the order of 700 nm is emitted from the lasing portion 40.Further, when a predetermined voltage is applied between the n-sideelectrode 33 in the second light emitting element 30 and the p-sideelectrode 57 via the pins 4 d and 4 c, a current is passed to the activelayer 53, light is emitted by recombination of electrons and holes, andlight having a wavelength in the band on the order of 600 nm is emittedfrom the lasing portion 50. The light goes out from the package 1through the light outgoing window 3 a of the package 1.

[0078] Although heat is also generated at the time of light emission,since the first substrate 21 is made of a material having relativelyhigh thermal conductivity, the heat generated by the lasing portion 40or 50 is promptly dissipated via the first substrate 21 and thesupporting base 11. The heat generated by the first light emittingelement 20 is promptly dissipated via the supporting base 11.

[0079] In the light emitting device 10A according to the embodiment asdescribed above, the first and second light emitting elements 20 and 30are stacked. It becomes therefore unnecessary to grow Group III-Vcompound semiconductor layers of the nitride system, and Group III-Vcompound semiconductor layers of the systems AlGaAs and AlGaInP on thesame substrate. Thus, the multiple-wavelength laser having a wavelengthof around 400 nm can be easily obtained. The use of the light emittingdevice 10A makes it possible to easily produce, for example, an opticaldisk drive capable of optical recording/playback using any optical diskby a plurality of kinds of light sources.

[0080] Especially, the first light emitting element 20 has a Group III-Vcompound semiconductor layer of the nitride system so as to emit lighthaving a wavelength of around 400 nm. Thus, by mounting the lightemitting device 10A on an optical device such as an optical disk drive,optical recording/playback using an optical disk on which information isrecorded at higher recording area density becomes possible.

[0081] Since the first substrate 21 is made of the material which istransparent in the visible region, the n-side electrode 29 and thewiring layer 13 can be formed with high positioning accuracy by usingthe lithography technique. By attaching the p-side electrodes 46 and 57in the second light emitting element 30 formed with high positioningaccuracy by using the lithography technique, the positions of the lightemitting regions of the first and second light emitting elements 20 and30 can be accurately controlled. Further, by setting each of theintervals to a predetermined small value, light emitted from each of thelight emitting elements is allowed to come out through a region of asmall diameter.

[0082] In addition, the first substrate 21 is made of the materialhaving high thermal conductivity, so that the heat generated at the timeof light emission in the lasing portions 40 and 50 can be promptlydissipated to the supporting base 11 via the first substrate 21. Thus,even when the second light emitting element 30 is disposed on the firstlight emitting element 20, the temperature of the light emitting element30 can be prevented from rising, so that the device can stably operatefor long time.

[0083] The light emitting device 10A is used for, for example, anoptical disk recording/playback apparatus as an optical device. FIG. 10schematically shows the configuration of the optical diskrecording/playback apparatus. The optical disk recording/playbackapparatus reproduces information recorded on an optical disk by usinglight of different wavelengths and records information onto an opticaldisk. The optical disk recording/playback apparatus has an opticalsystem for guiding outgoing light L_(out) having a predeterminedwavelength emitted from the light emitting device 10A to an optical diskD and reading signal light (reflection light L_(ref)) from the opticaldisk D under the control of the light emitting device 10A and a controlunit 111. The optical system has a beam splitter 112, a collimator lens113, a mirror 114, a quarter-wave plate 115, an objective lens 116, asignal light detection-lens 117, a signal light detection photoreceivingdevice 118, and a signal light reproducing circuit 119.

[0084] In the optical disk recording/playback apparatus, the outgoinglight L_(out) having, for example, strong intensity from the lightemitting device 10 is reflected by the beam splitter 112, made parallellight by the collimator lens 113, and reflected by the mirror 114. Theoutgoing light L_(out) reflected by the mirror 114 passes through thequarter-wave plate 115. After that, the outgoing light L_(out) iscondensed by the objective lens 116, and is incident on the optical diskD, thereby writing information onto the optical disk D. The outgoinglight L_(out) having, for example, weak intensity from the lightemitting device 10 passes through the optical components as describedabove and is incident on and reflected by the optical disk D. Thereflection light L_(ref) passes through the objective lens 116,quarter-wave plate 115, mirror 114, collimator lens 113, beam splitter112, and signal light detection lens 117, and is incident on the signallight detection photoreceiving device 118 where the light is convertedto an electric signal. After that, the information written on theoptical disk D is reproduced by the signal light reproducing circuit119.

[0085] As described above, the light emitting device 10A according tothe embodiment can be enclosed in a single package and the outgoinglight L_(out) is emitted from the plurality of light emitting regionsspaced accurately. By using the light emitting device 10A, the pluralityof outgoing light L_(out) of different wavelengths can be guided topredetermined positions by using the common optical system. Thus, thesmall, low-cost optical disk recording/playback apparatus having asimplified configuration can be realized. Since an error in the lightemitting point intervals is extremely small, the position of thereflection light L_(ref) forming an image in a photoreceiving portion(signal light detection photoreceiving device 118) can be prevented fromvarying according to optical disk recording/playback apparatuses. Thatis, the optical system can be easily designed and the yield of theoptical disk recording/playback apparatus can be improved.

[0086] The light emitting device 10A of the embodiment can realize lightemission of three wavelengths, that is, around 400 nm, in the range ofthe order of 600 nm, and in the range of the order of 700 nm. Thisenables optical recording/playback by using not only existing variousoptical disks such as CD-ROM (Read Only Memory), CD-R, CD-RW, MD, andDVD-ROM, but also what is called DVD-RAM (Random Access Memory), DVD+RW,DVD−R/RW and the like which are currently proposed as rewritablemass-storage disks. Further, optical recording/playback also becomespossible using next-generation recordable optical disks having higherrecording area density (for example, 20 G bytes or more) (such asoptical disks used for a DVR (Digital Video Recorder) or VDR (Video DiskRecorder) which are proposed as optical disk apparatuses of the nextgeneration). The use of such recordable mass-storage disks of the nextgeneration enables video data recording and reproduction of recordeddata (images) with high picture quality and excellent operability.

[0087] The description given above relates to an example in which thelight emitting device 10A is applied to the optical diskrecording/playback apparatus. However, obviously, the light emittingdevice 10A have extensive application to various optical apparatusessuch as optical disk playback apparatuses, optical disk recordingapparatuses, magnetooptic disk apparatuses for opticalrecording/playback using magnetooptical disks (MOs), and opticalcommunication systems. It can be also applied to equipment having avehicle-mounted semiconductor laser apparatus which has to operate athigh temperature, and the like.

Second Embodiment

[0088]FIG. 11 shows a sectional structure of a light emitting device 10Baccording to a second embodiment of the invention. The light emittingdevice 10B has the same configuration, action, and effects as those ofthe light emitting device 10A except that a second light emittingelement 60 is provided in place of the second light emitting element 30in the light emitting device 10A in the first embodiment. The samereference numerals are given to the same components as those of thefirst embodiment and their detailed description will not be repeated.

[0089] The second light emitting element 60 in the second embodiment hasthe same configuration as that of the second light emitting element 30except that a lasing portion 70 capable of emitting light having awavelength in the band on the order of 500 nm (for example, 520 nm) isprovided in place of the lasing portion 40 of the second light emittingelement 30 in the first embodiment and the buffer layer 32 is notprovided.

[0090] The lasing portion 70 has a configuration in which, for example,an n-type cladding layer 72, a guide layer 73, an active layer 74, aguide layer 75, a p-type cladding layer 76, a first p-type semiconductorlayer 77, a second p-type semiconductor layer 78, a p-type superlatticelayer 79, and a p-side contact layer 80 are laid one upon another in theorder named on the second substrate 31 on the side thereof on which thesupporting base 11 is disposed, with a buffer layer 71 in between. Eachof the layers is made of, for example, a Group II-VI compoundsemiconductor containing at least one element selected from the group ofGroup 2A or 2B elements in the short-period type periodic tableconsisting of zinc (Zn), cadmium (Cd), mercury (Hg), beryllium (Be) andmagnesium (Mg), and at least one element selected from the group ofGroup 6B elements in the short-period type periodic table consisting ofsulfur (S), selenium (Se) and tellurium (Te).

[0091] Specifically, the buffer layer 71 is made by depositing in orderan n-type GaAs film doped with silicon as an n-type impurity, a ZnSefilm doped with chlorine (Cl) as an n-type impurity, and a ZnSSe mixedcrystal layer doped with chlorine as an n-type impurity, from the sideof the second substrate 31. The thickness of the buffer layer 71 is, forexample, 100 nm. The n-type cladding layer 72 is, for example, 1 μmthick and is made of n-type ZnMgSSe mixed crystal doped with chlorine asan n-type impurity. The guide layer 73 is, for example, 0.1 μm thick andis made of n-type ZnSSe mixed crystal doped with chlorine as an n-typeimpurity or undoped ZnSSe mixed crystal. The active layer 74 is, forexample, 20 nm thick and has a multiple quantum well structure of a welllayer and a barrier layer which are made of Zn_(x)Cd_(1-x)Se (where x≧0)mixed crystal of different compositions. The active layer 74 functionsas a light emitting portion.

[0092] The guide layer 75 is, for example, 0.1 μm thick and is made ofp-type ZnSSe mixed crystal doped with nitrogen as a p-type impurity orundoped ZnSSe mixed crystal. The p-type cladding layer 76 has, forexample, 1.0 μm thick and is made of p-type ZnMgSSe mixed crystal dopedwith nitrogen as a p-type impurity. The first p-type semiconductor layer77 is, for example, 0.2 μm thick and is made of p-type ZnSSe mixedcrystal doped with nitrogen as a p-type impurity. The second p-typesemiconductor layer 78 is, for example, 0.2 μm thick and is made ofp-type. ZnSe doped with nitrogen as a p-type impurity. The p-typesuperlattice layer 79 is, for example, 35 nm thick and is formed byalternately depositing a p-type ZnSe film doped with nitrogen as ap-type impurity and a p-type ZnTe film doped with nitrogen as a p-typeimpurity. The p-side contact layer 80 is, for example, 0.1 μm thick andis made of p-type ZnTe doped with nitrogen as a p-type impurity.

[0093] A part of the first p-type semiconductor layer 77, second p-typesemiconductor layer 78, p-type superlattice layer 79, and p-side contactlayer 80 are formed in a narrow strip shape extending in the cavitydirection so that a current is restricted. On both sides of the stripportion, current block regions 81 are provided. The region in the activelayer 74 corresponding to the p-side contact layer 80 serves as a lightemitting region.

[0094] On the side of the p-type contact layer 80 opposite to the p-typesuperlattice layer 79, a p-side electrode 82 is formed. The p-sideelectrode 82 is formed by, for example, depositing in order palladium(Pd), platinum, and gold from the side of the p-side contact layer 80and alloying the deposited materials by heat treatment, and iselectrically connected to the p-side contact layer 80. The p-sideelectrode 82 is also electrically connected to the wiring layer 13 viathe adhesive layer 15.

[0095] The light emitting device 10B having such a configuration can bemanufactured in a manner similar to the first embodiment except that thesecond light emitting element 60 is formed in place of the second lightemitting element 30 in the light emitting device 10A.

[0096] Specifically, the second light emitting element 60 is produced asfollows. First, as shown in FIG. 12A, in a manner similar to the firstembodiment, for example, the buffer layer 51 made of n-type InGaP mixedcrystal, the n-type cladding layer 52 made of n-type AlGaInP mixedcrystal, the active layer 53 made of Al_(x)Ga_(y)In_(1-x-y)P (where x≧0and y≧0) mixed crystal, the p-type cladding layer 54 made of p-typeAlGaInP mixed crystal, and the p-type cap layer 55 made of p-type GaAsare grown in order on the surface of the second substrate 31 made ofn-type GaAs.

[0097] Subsequently, as shown in FIG. 12B, in correspondence with theregion in which the lasing portion 50 is to be formed, a mask M made ofsilicon dioxide or silicon nitride (Si₃N₄) is formed by, for example,CVD (Chemical Vapor Deposition) on the p-type cap layer 55. By using themask M, etching such as RIE (Reactive Ion Etching) is performed, therebyselectively removing the p-type cap layer 55, p-type cladding layer 54,active layer 53, n-type cladding layer 52, and buffer layer 51.

[0098] Subsequently, as shown in FIG. 13A, on the surface of the secondsubstrate 31, by MBE (Molecular Beam Epitaxy) for example, the bufferlayer 71 in which an n-type GaAs film, an n-type ZnSe film, and ann-type ZnSSe mixed crystal layer are deposited in the order named, then-type cladding layer 72 made of n-type ZnMgSSe mixed crystal, the guidelayer 73 made of n-type ZnSSe mixed crystal, the active layer 74 made ofZn_(x)Se_(1-x)Cd (where x≧0) mixed crystal, the guide layer 75 made ofp-type ZnSSe mixed crystal, the p-type cladding layer 76 made of p-typeZnMgSSe mixed crystal, the first p-type semiconductor layer 77 made ofp-type ZnSSe mixed crystal, the second p-type semiconductor layer 78made of p-type ZnSe, the p-type superlattice layer 79 in which a p-typeZnSe film and a p-type ZnTe film are alternately deposited, and thep-side contact layer 80 made of p-type ZnTe are grown in order. At thetime of growing each of the layers, the temperature of the secondsubstrate 31 is adjusted to, for example, about 280° C. After that, themask M is removed.

[0099] After removing the mask M, as shown in FIG. 13B, for example, amask (not shown) having an opening corresponding to the region in whichthe current block region 56 is to be created is formed, and an n-typeimpurity such as chlorine is introduced by ion implantation, therebyforming the current block regions 56. A mask (not shown) having anopening corresponding to the region in which the current block region 81is to be created is formed on the entire surface, and an n-type impuritysuch as chlorine is introduced by ion implantation to the p-side contactlayer 80, p-type superlattice layer 79, second p-type semiconductorlayer 78, and to the upper layer portion of the first p-typesemiconductor layer 77, thereby forming the current block region 81.Since the lithography technique is used here in a manner similar to thefirst embodiment the positions of the light emitting regions in thelasing portions 50 and 70 can be precisely defined.

[0100] After forming the current block regions 56 and 81, as shown inFIG. 14, on and around the surface of the p-type cap layer 55, forexample, titanium, platinum, and gold are vapor-deposited in order, tothereby form the p-side electrode 57. On and around the surface of thep-side contact layer 80, for example, palladium, platinum, and gold arevapor-deposited in order, to form the p-side electrode 82. Subsequently,a mask (not shown) is formed in correspondence with the region in whichthe lasing portions 50 and 70 are formed, and the portion from thep-side contact layer 80 to the buffer layer 71 is selectively removed.

[0101] After selectively removing the portion from the p-side contactlayer 80 to the buffer layer 71, the rear face side of the secondsubstrate 31 is, for example, lapped and polished to form the n-sideelectrode 33 on the rear face side of the second substrate 31 in amanner similar to the first, embodiment. Subsequently, heat treatment isperformed to alloy the p-side electrodes 57 and 82 and the n-sideelectrode 33. Finally, the second substrate 31 is cleaved in apredetermined width perpendicularly to the longitudinal direction of thep-side electrodes 57 and 82, and a pair of not-shown reflecting mirrorfilms are formed on the cleaved faces. In such a manner, the secondlight emitting element 60 is fabricated.

[0102] Since the light emitting device 10B according to the embodimenthas the first light emitting element 20 capable of emitting light in theband on the order of 400 nm and the second light emitting element 60having the lasing portion 70 capable of emitting light in the band onthe order of 500 nm and the lasing portion 50 capable of emitting lightin the range of the order of 700 nm, the light emitting device foremitting light of three primary colors of red (R), green (G), and blue(B) can be realized. The light emitting device 10B can be used as alight source of not only the optical disk drive but also full-colordisplays.

[0103] In the case of using the light emitting device 10B as lightsources of full-color displays, by adjusting the composition of thematerial of each of the active layers 23, 53, and 74 as appropriate,light emitted from each of the light emitting portions can have adesired hue.

[0104]FIG. 15 shows a schematic configuration of a display 120 using thelight emitting device 10B according to the embodiment. The display 120has a board 121 and a plurality of light emitting devices 10B accordingto the embodiment provided on one face of the board 121. For example,each of the light emitting devices 10B is enclosed in the package 1 asshown in FIG. 5 and the light emitting devices 10B are arranged in amatrix of M rows and N columns (where, M and N are natural numbers).Although not shown in FIG. 15, on the board 121, common lines 122 and123 in the column direction and common lines 124 and 125 in the rowdirection are formed.

[0105]FIG. 16 shows a schematic configuration of a driving circuit ofthe display 120. The supporting base 11 of each of the light emittingdevices 10B is connected to the common line 122 in the column directionvia a wire, and the n-side electrode 33 in the second light emittingelement 60 is connected to the common line 123 in the column directionvia a wire. The wiring layer 13 is connected to the common line 124 inthe row direction, and the n-side electrode 29 in the first lightemitting element 20 is connected to the common line 125 in the columndirection via a wire. The common lines 122 to 125 are connected to acontrol unit (not shown) and a desired color is displayed according to asignal from the control unit.

[0106] The light emitting device 10B of the second embodiment acts in amanner similar to the light emitting device 10A of the first embodimentexcept that, when a voltage is applied between the n-side electrode 33and the p-side electrode 82 via the pins 4 d and 4 b of the package 1(FIG. 5), a current is passed to the active layer 74, light is emittedby recombination of electrons and holes, and light having a wavelengthin the band on the order of 500 nm is emitted from the lasing portion70.

Third Embodiment

[0107]FIG. 17 shows a sectional structure of a light emitting device 10Caccording to a third embodiment of the invention. The light emittingdevice 10C has the same configuration, action, and effects as those ofthe light emitting device 10A of the first embodiment except that afirst light emitting element 90 is provided in place of the first lightemitting element 20 in the light emitting device 10A of the firstembodiment, and a supporting base 17 is provided in place of thesupporting base 11. The same reference numerals are given to the samecomponents as those of the first embodiment and their detaileddescription will not be repeated here.

[0108] The first light emitting element 90 is largely different from thefirst light emitting element 20 with respect to the point that adifferent material is used for a first substrate 91. For example, thefirst substrate 91 is made of sapphire having a thickness of about 80μm. Sapphire is an insulating material and is transparent in the visibleregion like GaN. The first light emitting element 90 has a configurationin which, for example, on the c-cut plane of the first substrate 91; ann-side contact layer 93, the n-type cladding layer 22, the active layer23, the degradation preventing layer 24, the p-type cladding layer 25,and the p-type contact layer 26 are laid one upon another in the ordernamed from the side of the first substrate 91 with a buffer layer 92 inbetween. The insulating layer 27 is formed on the surface of the p-typecladding layer 25 and the side faces of the p-side contact layer 26, andthe p-side electrode 28 is formed on the side of the p-side contactlayer 26 opposite to the p-side cladding layer 25.

[0109] The buffer layer 92 has, for example, 30 nm thick and is made ofundoped GaN or n-type GaN doped with silicon as an n-type impurity. Then-side contact layer 93 is, for example, 5 μm thick and is made ofn-type GaN doped with silicon as an n-type impurity.

[0110] The n-side contact layer 93 has an exposed portion in which then-type cladding layer 22, the active layer 23, the degradationpreventing layer 24, the p-type cladding layer 25, and the p-sidecontact layer 26 are not formed. In the exposed portion, for example, ann-side electrode 94 in which titanium and aluminum are deposited inorder from the side of the n-side contact layer 93 and alloyed by heattreatment is formed. In the embodiment, the insulating film 27 isprovided so as to cover also the side faces of the p-type cladding layer25, degradation preventing layer 24, active layer 23, and cladding layer22.

[0111] The supporting base 17 is made of an insulating material havinghigh thermal conductivity such as aluminum nitride (AlN). On one face ofthe supporting base 17, a wiring layer 17 a made of a metal is providedin correspondence with the p-side electrode 28 in the first lightemitting element 90, and a wiring layer 17 b made of a metal is providedin correspondence with the n-side electrode 94. The p-side electrode 28and the wiring layer 17 a are attached to each other with the adhesionlayer 12 in between, and the n-side electrode 94 and the wiring layer 17b are attached to each other with an adhesion layer 18 in between.

[0112] On the side of the first substrate 91 opposite to the supportingbase 17, the wiring layer 13 is provided in a manner similar to thefirst embodiment, and a wiring layer 19 made of a metal is provided forconnecting the lasing portion 50 to the external power source isprovided in place of the n-side electrode 29 in the first embodiment.

[0113] The light emitting device 10C is used by, for example, beingenclosed in a package in a manner similar to the first embodiment. Inthe package, a placement stage is provided on one face of the supportingbody, and the supporting base 17 is placed on the placement stage. Thepackage has, for instance, five pins which are electrically connected tothe wiring layers 13, 17 a, 17 b , and 19 and the n-side electrode 33via wires. In this case as well, the number of pins can be set asappropriate in a manner similar to the first embodiment.

[0114] The light emitting device 10C can be manufactured as follows.

[0115] First, as shown in FIG. 18A, for example, the first substrate 91made of sapphire having a thickness of about 400 μm is prepared. On thec-cut plane of the first substrate 91, the buffer layer 92 made ofundoped GaN or n-type GaN is grown. At this time, the temperature of thefirst substrate 91 is set to, for example, 500° C. Subsequently, on thebuffer layer 92, the n-type contact layer 93 made of n-type GaN, then-type cladding layer 22 made of n-type AlGaN mixed crystal, the activelayer 23 made of InGaN mixed crystal, the degradation preventing layer24 made of p-type AlGaN mixed crystal, the p-type cladding layer 25 madeof p-type AlGaN mixed crystal, and the p-side contact layer 26 made ofp-type GaN are grown in order. At the time of growing each of thelayers, the temperature of the first substrate 91 is adjusted to anappropriate temperature, for example, from 750 to 1100° C.

[0116] As shown in FIG. 18B, the p-side contact layer 26, p-typecladding layer 25, degradation preventing layer 24, active layer 23, andn-type cladding layer 22 are etched in order; to expose a part of then-side contact layer 93. After that, a not-shown mask is formed and, byusing the mask, the upper layer portion in the p-type cladding layer 25,and the p-side contact layer 26 are formed in a narrow strip shape by,for example, RIE.

[0117] The insulating layer 27 made of silicon dioxide is formed on theside faces of the layers of which part is selectively etched and on thesurface of the p-type cladding layer 25 by, for example, vapordeposition. After that, the rear face side of the first substrate 91 islapped and polished so that the thickness of the first substrate 91becomes, for example, about 100 μm.

[0118] After thinning the first substrate 91, on the side of the firstsubstrate 91 opposite to the buffer layer 92, the wiring layers 13 and19 are formed in predetermined positions. In a manner similar to thefirst embodiment, the first substrate 91 is made of the materialtransparent in the visible region, so that the positions in which thewiring layers 13 and 19 are formed can be precisely controlled.

[0119] Subsequently, for instance, nickel, platinum, and gold arevapor-deposited in order on and around the surface of the p-side contactlayer 26 to form the p-side electrode 28. For example, titanium andaluminum are vapor-deposited in order on the surface of the n-sidecontact layer 93 to thereby form the n-side electrode 94. Further, byconducting heat treatment, the p-side electrode 28 and the n-sideelectrode 94 are alloyed. After that, though not shown here, the firstsubstrate 91 is, for example; cleaved in a predetermined widthperpendicular to the longitudinal direction of the p-side electrode 28,and a pair of reflecting mirror films are formed on the cleaved faces.In such a manner, the first light emitting element 90 is fabricated.

[0120] After that, in a manner similar to the first embodiment, thesecond light emitting element 30 is fabricated.

[0121] The supporting base 17 on which wiring layers 17 a and 17 b areformed is prepared, the p-side electrode 28 in the first light emittingelement 90 and the wiring layer 17 a are attached to each other with theadhesive layer 12 in between, and the n-side electrode 94 and the wiringlayer 17 b are attached to each other with the adhesive layer 18 inbetween. The p-side electrode 46 in the second light emitting element 30and the wiring layer 13 are attached to each other with the adhesivelayer 15 in between, and the p-side electrode 57 and the wiring layer 19are attached to each other with the adhesive layer 16 in between. Insuch a manner, the light emitting device 10C is completed.

[0122] In the light emitting device 10C according to the embodiment, thefirst substrate 91 is made of sapphire which is transparent in thevisible region, so that the light emitting regions of the first andsecond light emitting elements 90 and 30 can be precisely controlled ina manner similar to the first embodiment.

[0123] Although the invention has been described above by theembodiments, the invention is not limited to the embodiments but can bevariously modified. In the foregoing embodiments, the specific stackedstructures of the first light emitting elements 20 and 90 and the secondlight emitting elements 30 and 60 have been described as examples. Theinvention is similarly applied to the case where the first lightemitting elements 20 and 90 or second light emitting elements 30 and 60have other structures. For example, the first light emitting element mayhave a construction to restrict a current by current block regions in amanner similar to the second light emitting elements 30 and. 60. Thesecond light emitting element may have a construction to narrow acurrent by an insulating film made of silicon dioxide or the like in amanner similar to the first light emitting elements 20 and 90. Althougha ridge-guiding type semiconductor laser in which gain-guiding type andrefractive index-guiding type are combined has been described as anexample in the foregoing embodiments, the invention can be similarlyapplied to a gain-guiding type semiconductor laser and a refractiveindex-guiding type semiconductor laser.

[0124] Further, in the foregoing embodiments, the case where the layersmade of GaN, AlGaAs, and AlGaInP compounds are formed by MOCVD has beendescribed. The layers may be formed by other vapor phase epitaxy such asMBE or hydride vapor phase epitaxy. The hydride vapor phase epitaxy isvapor phase epitaxy in which halogen contributes to transport orreaction. Although the case where the layers made of ZnSe compounds areformed by MBE has been described in the second embodiment, the layersmay be formed by other phase vapor epitaxy such as MOCVD.

[0125] In addition, although the specific examples regarding thematerials of the first substrates 21 and 91 in the first light emittingelements 20 and 90 have been described, other materials may be alsoused. It is preferable to use a material which is transparent in thevisible region, since effects described in the foregoing embodiments areobtained. More preferably, a material having high thermal conductivityis used. Examples of such materials are aluminum nitride and siliconcarbide (SiC).

[0126] Further, in the third embodiment, the case where the second lightemitting element 30 having the lasing portion 40 of the system AlGaAsand the lasing portion 50 of the system AlGaInP is provided has beendescribed. Alternatively, the second light emitting element 60 describedin the second embodiment may be provided.

[0127] Further, in the foregoing embodiments, the case where the firstlight emitting element 20 (90) and the second light emitting element 30(60) emit light of different wavelengths has been described. A pluralityof the first light emitting element 20 (90) can be stacked on one faceof the supporting base 11 (17). Further, a plurality of light emittingelements of different characteristics or structures can be stacked. Inthis case, the wavelengths may be the same or different from each other.In the case of stacking a plurality of light emitting elements ofdifferent characteristics, for example, a low-output device and ahigh-output device can be mixedly used.

[0128] Although the case where the first light emitting element 20 (90)has one light emitting portion has been described in the foregoingembodiments, the first light emitting element 20 (90) may have aplurality of light emitting portions, specifically, a plurality oflasing portions in a manner similar to the second light emitting element30. In this case, the wavelengths of the lasing portions may be the sameor different from each other. The characteristics or structures may bethe same or different from each other.

[0129] Further, in the embodiments, the case where the second lightemitting element 30 (60) has two lasing portions has been described. Thenumber of the lasing portions of the second light emitting element maybe one or three or more. The wavelengths, characteristics, or structuresof the lasing portions may be the same or different from each other.

[0130] In addition, although the case where each of the second lightemitting elements 30 and 60 is what is called a monolithic typemultiple-wavelength laser has been described in the foregoingembodiments, the invention can be also applied to the case where thesecond light emitting element is what is called a hybrid typemultiple-wavelength laser as shown in FIG. 2.

[0131] Further, although the specific examples regarding the materialsof the supporting bases 11 and 17 have been described in the foregoingembodiments, other materials may be also used. However, a materialhaving high thermal conductivity is preferable. Although the supportingbase 11 is made of a metal in the first and second embodiments, in amanner similar to the third embodiment, the supporting base may be madeof an insulating material and a wire may be provided on the supportingbase.

[0132] In addition, although the supporting base 11 (17) is directlysupported by the supporting body 2 at the time of housing the lightemitting device in the package 1 in the foregoing embodiments, it isalso possible to provide a placement stage for the supporting body 2 andplace the supporting base 11 (17) on the placement stage.

[0133] Although a semiconductor laser has been-described as a specificexample of the light emitting element in the embodiments, the inventioncan be also applied to a light emitting device having other lightemitting element such as a light emitting diode (LED).

[0134] According to the light emitting device of the invention, sincethe plurality of light emitting elements are stacked on one face of thesupporting base, it is unnecessary to dispose a plurality of lightemitting elements on the same substrate, and the device can be easilymanufactured.

[0135] Especially, according to the light emitting device of one aspectof the invention, the first substrate is transparent in the visibleregion, so that the positions of the light emitting regions in the firstand second light emitting elements can be precisely controlled.

[0136] Moreover, according to the light emitting device of one aspect ofthe invention, the first light emitting element has a semiconductorlayer containing at least one of Group 3B elements and at least nitrogen(N) from Group 5B elements, so that the first light emitting element canemit light of a wavelength around 400 nm. Consequently, when the lightemitting device is mounted on an optical device, an optical devicehaving higher performance can be realized.

[0137] Further, according to the light emitting device of one aspect ofthe invention, the first substrate is made of either a Group III-Vcompound semiconductor of the nitride system containing at least one ofGroup 3B elements and at least nitrogen from Group 5B elements, orsapphire. Heat generated at the time of light emission in the secondlight emitting element can be therefore promptly dissipated via thefirst substrate. Thus, a temperature rise in the second light emittingelement can be prevented and the device can operate stably for longtime.

[0138] In addition, the optical device according to the invention isconstructed by using the light emitting device of the invention.Consequently, higher performance can be achieved and reduction in sizeand cost can be realized.

[0139] Obviously many modifications and variations of the presentinvention are possible in the light of the above teachings. It istherefore to be understood that within the scope of the appended claimsthe invention may be practiced otherwise than as specifically described.

What is claimed is:
 1. A light emitting device having a plurality oflight emitting elements stacked on one face of a supporting base.
 2. Alight emitting device comprising: a supporting base; a first lightemitting element having a first substrate, provided on one face of thesupporting base; and a second light emitting element having a secondsubstrate, provided on the side of the first light emitting elementopposite, to the supporting base.
 3. A light emitting device accordingto claim 2, wherein the first substrate is transparent in the visibleregion.
 4. A light emitting device according to claim 2, wherein thefirst and second light emitting elements can emit light of differentwavelengths.
 5. A light emitting device according to claim 2, whereinthe first light emitting element has a semiconductor layer containing atleast one of Group 3B elements and at least nitrogen (N) from Group 5Belements.
 6. A light emitting device according to claim 5, wherein thefirst substrate is made of either a Group III-V compound semiconductorof the nitride system containing at least one of Group 3B elements andat least nitrogen (N) from Group 5B elements, or sapphire (Al₂O₃).
 7. Alight emitting device according to claim 2, wherein the first lightemitting element has a light emitting portion on the first substrate onthe side thereof on which the supporting base is disposed.
 8. A lightemitting device according to claim 2, wherein the second light emittingelement has a light emitting portion on the second substrate on the sidethereof on which the first light emitting element is disposed.
 9. Alight emitting device according to claim 2, wherein the second lightemitting element has a plurality of light emitting portions of differentoutput wavelengths.
 10. A light emitting device according to claim 2,wherein the second substrate is made of gallium arsenide (GaAs).
 11. Alight emitting device according to claim 2, wherein the second lightemitting element has a semiconductor layer containing at least gallium(Ga) from Group 3B elements and at least arsenide (As) from Group 5Belements.
 12. A light emitting device according to claim 2, wherein thesecond light emitting element has a semiconductor layer containing atleast indium (In) from Group 3B elements and phosphorus (P) from Group5B elements.
 13. A light emitting device according to claim 2, whereinthe second light emitting element has a semiconductor layer containingat least one element selected from the group of Group 2A or 2B elementsconsisting of zinc (Zn), cadmium (Cd), mercury (Hg), beryllium (Be) andmagnesium (Mg), and at least one element selected from the group ofGroup 6B elements consisting of sulfur (S), selenium (Se) and tellurium(Te).
 14. An optical device having a light emitting device in which aplurality of light emitting elements are stacked on one face of asupporting base.
 15. An optical device on which a light emitting deviceis mounted, the light emitting device comprising: a supporting base; afirst light emitting element having a first substrate, provided on oneface of the supporting base; and a second light emitting element havinga second substrate, provided on the side of the first light emittingelement opposite to the supporting base.